Protein malnutrition is a significant problem in patients with chronic renal failure (CRF) and in patients maintained on hemodialysis (HD). We hypothesize that protein metabolism (synthesis or degraduation) is influenced by the degree of renal failure and by the amount of protein intake; and protein metabolism in muscle and liver is influenced by the type of dialyzer membrane used during HD. There was no patient activity in the last year, as the study closed to enrollment. Analysis of the samples and data will continue in the Biomedical Mass Spectrometry Core laboratory.